| 18 | adj. |
| 18th | adj. |
| 1820s | (n) the decade from 1820 to 1829 |
| 1830s | (n) the decade from 1830 to 1839 |
| 1840s | (n) the decade from 1840 to 1849 |
| 1850s | (n) the decade from 1850 to 1859 |
| 1860s | (n) the decade from 1860 to 1869 |
| 1870s | (n) the decade from 1870 to 1879 |
| 18-karat gold | (n) an alloy that contains 75 per cent gold |